<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
		.wrap{display:flex;}
		.fixed {background-color:#FF6B4B;}
		.middle{flex:1; background-color:#9ECAF0;}
	</style>
</head>
<body>
	<div class="wrap">
		<div class="fixed">固定宽度</div>
		<div class="middle">自适自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应应</div>
		<div class="fixed">固定宽度</div>
	</div>

<div>方法2</div>
<div style="float:left; width:120px;background:#ff6b4b">固定</div>
<div style="float:left; margin-left:120px;background:#fa6b4b">自适自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应自适应应</div>
<div style="float:right; width:120px;background:#ff6b4b;">固定</div>
	


</body>
</html>